Prime Minister Benjamin Netanyahu's security cabinet voted for the move early on Tuesday.
UN Middle East envoy Nickolay Mladenov said this while briefing media after U.N. Security Council meeting behind closed doors.
"The dangers on the ground will escalate if we go through another cycle of Friday Prayer without a resolution to this current crisis", he said.
Rival Palestinian factions Fatah and Hamas have issued calls for mass protests by Muslims against Israel on Friday over security measures instated at a contested Jerusalem holy site. Israeli police spokesman Micky Rosenfeld said there were no confrontations on Wednesday, and that some Muslims were entering the site to pray.
Israel has denied it has a hidden agenda, portraying the metal detectors as a needed security measure.
Deadly unrest has erupted since the new measures were introduced, with clashes breaking out around the compound and in the occupied West Bank, leaving five Palestinians dead.
The tensions surrounding the site were also cited by assailants in two recent terror attacks, including last week when a Palestinian stabbed to death three members of the Salomon family in the West Bank settlement of Halamish as they celebrated Shabbat.
Maj. Gen. Yoav Mordechai, who heads the Israeli defense body for Palestinian civilian affairs, said Israel was open to alternatives to lower the tensions.More news: How technical signals have emerged? - Teck Resources Limited (TECK), KBR, Inc. (KBR)
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Israel put the devices in place on July 16, two days after two Israeli policemen were shot and killed by Israeli-Arab attackers who had concealed weapons in the compound in the heart of the Old City. A top adviser to Palestinian President Mahmoud Abbas said he was holding consultations with various countries, including Jordan, Saudi Arabia, Egypt and Morocco, about the crisis.
Israel has removed the controversial metal detectors from entrances to the sensitive compound that is home to the al-Aqsa mosque.
The Palestinians were furious about the metal detectors, accusing Israel of violating freedom of worship and trying to seize control of the third holiest place in Islam.
The king stressed "the need to find an immediate solution and remove the reasons for the ongoing crisis at the Haram al-Sharif compound", the statement said. Instead of metal detectors, Israel plans to install unspecified advanced technologies and "smart inspection". Jordan relented and embassy personnel left Amman on Monday for Israel as the decision to remove the detectors was announced.
"Israel is mistaken in the steps it has taken and - I will say this very openly - is heading into isolation", he warned. The clock was ticking, with last week's main weekly Muslim prayers on Friday having brought the situation to a boil. Israeli police said they were investigating the charge.
"We can not rely on anyone", he said, bemoaning what he said is the ineffectiveness of Abbas and his Palestinian Authority government in the West Bank.
"At the holy sites, it's vital that both access and security be ensured". It has been a flashpoint site for Israeli-Palestinian conflict in the past decades since the 1967 Israeli occupation of East Jerusalem.
Palestinians in Jerusalem, who see themselves as the defenders of the holy site, felt Israel crossed a red line with its latest measures.